After installing the drivers and software for a 5" HDMI display and updating the pi, we got an "end kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block (179,2)" error on boot up.

That means your filesystem is screwed and needs a fsck run on it. Nothing to do with HDMI, it's more likely caused by pulling the power.

Get another SDCard and USB reader. Download Raspbian Stretch and Etcher. Use Etcher to write Raspbian to the new SDCard. Boot that. Mount the bad SDCard in the USB reader. Open an LXTerminal window and run the following